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ing a methyl group are decomposed on heating with zinc chloride,
indoles being formed with elimination of ammonia. (E. Fischer.)
GIL                          |    '
I                    ,NII  C
C,,H5Nir.N:C       = O'll/           !| + NIL
I                  X -- CII
Acetone-phenylhydra/.onc.             Methyl iudole.
Sulphanilic Acid. The acid characters of this substance,
which is both base and acid, are more prominently developed
than the basic character. Nevertheless it reacts with nitrous
acid like a primary amine, and forms a diazonium salt, which
has the following constitution (see Prep. 62, p. 161) : 
/N : N
QH/         I
Dia/obenzene sulphonic acid.
The formation of suphanilic acid is probably preceded by the
sulphonation of the amino-group,
A compound of this character has been obtained which
decomposes with acids into o- and ^-aminosulphonic acid by
a process of intramolecular change (Bamberger). The fact of
the para-compound being exclusively formed at the higher
temperature may account for the production of this substance
in the present preparation.
Methyl Orange .--The first point to notice in this reaction
is that the diazonium salt forms no diazoamino-compound with
the dimethylanilme, but at once produces an azo-compound.
This is always the case with tertiary amines, some secondary
amines like diphenylamine and the phenols. The reaction may
be regarded as typical of the formation of all azo-colouring
matters. At least two substances are requisite in this process ;
on the one hand an aromatic compound containing an amino-
group in the nucleus, and, on the other, a base or phenol
COT EN'S ADV. P. O. C                                                          U